Fix kmix icon change on muting/unmuting

This resolves Bug 1505

kmix/kmixdockwidget.cpp

@@ -376,6 +376,7 @@ KMixDockWidget::dockMute()
 		if ( md != 0 ) {
         		md->setMuted( !md->isMuted() );
         		m_mixer->commitVolumeChange( md );
+        		updatePixmap(false);
 		}
 	}
 }